The need to supply a variable degree of drag when playing a fish has long been recognized. As a result, fishing reels traditionally have incorporated into their design means for supplying this variable drag.
Variable drag is achieved by providing a variable resistance affecting the amount of tension a reel will accept before allowing line to be paid out. Too little resistance will allow a fish too much and the chance to let the line fall slack or the reel to over run and tangle. A slack line can allow the fish to spit the hook, to recuperate or to change position underwater such that the line may be snagged and broken. Too much resistance will allow the fish to break the line through a sudden move providing momentary force greater than the tensile strength of the line. Such a sudden move may not be adequately compensated for by the drag adjustment.
The importance of the drag adjustment is apparent, as should be the fact that the same adjustment does not apply to all fish and that when playing a large game fish the requirements will change over a period of time or even from moment to moment. When a fish breaches and then tries to dart in a different direction, the demands on the line, and desired drag adjustment, will differ from those when the fish is running or being walked in. Adjustment must be made manually and is distracting. Additionally, continual adjustment, reacting as the fish moves, is not feasible with the traditional drag systems.
Inherent to conventional drag mechanism designs are relatively non-instantaneous functional aspects. As such, traditional reels make it difficult, if not impossible, to optimize the desired balance between the fish's strength, the breaking strength of the fishing line and setting the drag to allow a fish to run and tire. Thus, with traditional reels, a fisherman adjusting the drag while playing a fish must suffer a lag time in the adjustment to the unpredictable and impulsive motions of a hooked fish or is forced to try to anticipate such moves, all too often resulting in "the one that got away".